The following description relates to a filter assembly.
An ink jet printer typically includes an ink path from an ink supply to an ink nozzle assembly including nozzle openings from which ink drops are ejected. Ink drop ejection can be controlled by pressurizing ink in the ink path with an actuator, which may be, for example, a piezoelectric deflector, a thermal bubble jet generator, or an electrostatically deflected element. A typical printhead has an array of ink paths with corresponding nozzle openings and associated actuators, and drop ejection from each nozzle opening can be independently controlled. In a so-called “drop-on-demand” printhead, each actuator is fired to selectively eject a drop at a specific pixel location of an image, as the printhead and a printing media are moved relative to one another. In high performance printheads, the nozzle openings typically have a diameter of 50 microns or less (e.g., 25 microns), are separated at a pitch of 100-300 nozzles per inch, have a resolution of 100 to 3000 dpi or more, and provide drop sizes of approximately 1 to 70 picoliters (pl) or less. Drop ejection frequency is typically 10 kHz or more.
A printhead can include a semiconductor printhead body and a piezoelectric actuator, for example, the printhead described in Hoisington et al., U.S. Pat. No. 5,265,315. The printhead body can be made of silicon, which is etched to define ink chambers. Nozzle openings can be defined by a separate nozzle plate that is attached to the silicon body. The piezoelectroic actuator can have a layer of piezoelectric material that changes geometry, or bends, in response to an applied voltage. The bending of the piezoelectric layer pressurizes ink in a pumping chamber located along the ink path.
Printing accuracy can be influenced by a number of factors, including the size, velocity and uniformity of ink drops ejected by the nozzles in the printhead and among the multiple printheads in a printer. The drop size and drop velocity uniformity are in turn influenced by factors, such as the dimensional uniformity of the ink paths, acoustic interference effects, contamination in the ink flow paths, and the actuation uniformity of the actuators. Contamination in the ink flow can be reduced with the use of one or more filters in the ink flow path. Typically, a filter is included upstream of the ink chambers, at an interface of an ink reservoir and the printhead, if the reservoir is removable, or is included within or at the reservoir.
In some applications, the ink is recirculated from the ink source to the printhead and back to the ink source, for example, to prevent coagulation of the ink and/or to maintain the ink at a certain temperature above the ambient temperature, for example, by using a heated ink source.